This invention relates to comparative topographical mapping and in particular to a method and means for remotely and non-destructively obtaining three dimensional topographical data from an object using a two dimensional scene recording device.
Manufacturers may soon have available the technology to entirely automate the fabrication of products containing complex subsystems and complicated surface geometries. The potential technology for automated fabrication is called "Autoreplication". In its ultimate form, Autoreplication will permit any existing object to be rapidly and automatically replicated in any specified material, and any idea for a shape or form could be automatically transformed into a real object. Autoreplication may shorten the lead time between initial design and finished product, enlarge production capacity, conserve materials, maximum product performance, permit the use of new materials and fabricating methods, and reduce unit manufacturing cost.
In the medical area, Autoreplication may lead to new reconstructive surgical techniques, in which the surgeon requests and receives precisely replicated human structures custom manufactured during the surgical procedure. The replicated structures would then be surgically placed for functional or esthetic restoration.
The automated replication concept, however, requires a device capable of automatically inspecting any specified object, from a distance, and rapidly providing numerical spatial data (i.e., three-dimensional spatial coordinates) which mathematically defines, in three-dimensional space, any surface or surfaces comprising the object. Given such a device, precise numerical coordinate `maps` could be sequentially produced of the original object or object design, the material being processed, and the finished products. To date, the lack of such a universal spatial mapping and comparison device has been a limiting factor in any proposal to automate the replication of any unknown, arbitrarily curved object.
The various state-of-the-art approaches to providing remote topographical data have, in general, proven unsatisfactory. A two-dimensional television or photographic image of a scene usually contains insufficient information for a three-dimensional reconstruction of the scene. To obtain the additional information needed for three-dimensional mapping, a scene can be analyzed passively by stereophotogrammetry or actively by introducing coded illumination. Generally, stereophotogrammetry requires a human operator to determine corresponding scene positions in different photographs, and is therefore too slow for real-time applications. Automated stereo methods require considerable analysis. Methods of actively interrogating a scene (by applying various kinds of light to the scene) have been used in recent years. Holography requires the interference of phase coherent light beams (one beam scattered off the scene and one reference beam) but post-analysis is often difficult. Although three-dimensional information has been obtained from illumination of the scene from different directions and by the application of light grids and light strips it does not appear that these methods have been used for portable real-time surface mapping applications.
Furthermore, these methods are not completely automatic and cannot provide mathematically unambiguous surface topography. Also, laser rangefinder which illuminates only one point at a time are too cumbersome for many applications.
There currently exists the need, therefore, for a comparative topographic mapping device that will automatically inspect any specified object, at significant distances, and rapidly provide numerical spatial data which mathematically defines, in three-dimensional space, any surface or surfaces comprising the object. The present invention is directed toward satisfying that need.